1. Field of the Invention
The present invention relates to a method of fabricating a liquid crystal display device that prevents breakage of a substrate during a scribing process.
2. Discussion of the Related Art
A liquid crystal display (LCD), which has advantages including a high contrast ratio and low power consumption, and which is suitable for gray scale or moving picture displays, has become a substitute for a cathode ray tubes (CRTs) so as to overcome the disadvantages associated with cathode ray tubes.
Generally, such a liquid crystal display device includes a thin film transistor substrate having thin film transistors and pixel electrodes formed in pixel areas defined by gate and data lines, respectively; a color filter substrate having a color filter layer and a common electrode formed thereon; and a liquid crystal layer formed between the two substrates. The liquid crystal display device receives various external signals so as to display an image.
Recently, a thin and lightweight device has been developed for liquid crystal panel applications such as mobile phones, personal digital assistants (PDAs), and notebook computers.
There are various methods for reducing the weight of the liquid crystal display device. It is most preferable that a large-sized glass substrate, which is the heaviest component of the liquid crystal display device, is thinned to reduce the weight of the LCD device.
A method of fabricating a liquid crystal display device according to a related art is explained in reference to the drawings as follows.
FIG. 1 illustrates a flowchart of a method of fabricating a liquid crystal display device according to a related art. FIG. 2 illustrates a layout of a liquid crystal display device according to a related art. FIG. 3 illustrates a method for forming sealing patterns according to the related art.
Referring to FIG. 1, a thin film transistor substrate having thin film transistors and pixel electrodes formed in pixel areas defined by gate and data lines, respectively and a color filter substrate having a color filter layer and a common electrode formed thereon are provided in (S1).
A sealant 14 in FIG. 2 is formed on the thin film transistor or color filter substrate so as to be an adhesive agent between the thin film transistor and color filter substrate. Spacers are scattered on the thin film transistor or color filter substrate so as to maintain a uniform interval between the two substrates. The thin film transistor and color filter subtrates are then bonded to each other so as to face each other (S2).
The sealant 14, as shown in FIG. 2 is formed at circumferences of effective display areas that will display an image, respectively, thereby forming a cell gap as well as preventing leakage of liquid crystals.
Dummy patterns 15 are formed simultaneously when the sealant 14 is formed. The dummy patterns 15 are formed between the sealant 14 in parallel with a scribing line, which will be formed later, so as to absorb shocks generated from scribing/breaking processes.
Specifically, the sealant 14 and the dummy patterns 15 are formed by a process such screen printing using an adhesive agent mixed with micro-pearls and the like.
In FIG. 3, a screen mask 51 is placed on a substrate 52. An adhesive agent 53 is dropped on the screen mask 51. Then the adhesive agent 53 is pushed in one direction by a squeegee 54. Thus, the adhesive agent is printed on the substrate 52 through an opening 51a of the screen mask 51 so as to form each of the sealant 14.
After the sealant 14 has been formed, the other substrate is bonded to the substrate 52 so as to face each other. Hot pressure is applied to the two substrates so as to harden the sealant, whereby the two substrates are fully bonded to each other.
Subsequently, surfaces of the substrates are etched so as to thin the device (S3).
In accordance with the trend of thinning the device, substrate etching techniques for decreasing the thickness of the substrate are available. In order to decrease the thickness of the substrate, an outer surface of the substrate is grinded or a glass substrate is dipped in an etching container filled with an etchant solution so that a surface of the substrate is etched.
The latter method of etching the substrate is carried out in a manner that a liquid crystal display panel prepared by bonding substrates to each other is dipped in an etching container filled with HF. Hence, outer surfaces of the substrates are etched uniformly.
In order to cut the substrates into designated sizes, successively scribing lines 18 in FIG. 2 are formed on a surface of the color filter or thin film transistor substrate using a scribing wheel having constant pressure and speed.
After the scribing lines have been formed, force is directly applied along the scribing lines using a break bar so as to separate the liquid crystal display panel. In this case, caution should be used so that the force is not concentrated on a local position (S4).
After the scribing/breaking processes, a physical process using an air blower is carried out so as to remove the debris from the liquid crystal display panel.
The number of times that scribing/breaking is used to separate the small-sized LCD panel is greater than that of a general or large-sized LCD panel, and the strength of the small-sized LCD panel is weaker than that of the general or large-sized LCD panel. Hence, the substrate is broken with ease. Specifically, such a problem occurs severely at an intersection “A” in FIG. 2 between the scribing lines.
Subsequently, a liquid crystal layer is formed between the two substrates (S5), and cut faces and edges of the liquid crystal display panel are grinded using an abrasive grindstone having a predetermined mesh (S6).
The liquid crystal layer is formed by providing a vacuum state inside the liquid crystal cell and injecting liquid crystals between the two substrates using capillary action.
Finally, a cleaning process is carried out so as to remove the liquid crystals, particles, and substrate debris adhered to an outer surface of the panel. Then a failure of the panel is determined by inspecting an exterior of the panel or applying an electric signal thereto.
Thereafter, a module assembly is carried out in such a manner that a polarizing plate is attached to the outer surface of the liquid crystal display panel, an external driving circuit is connected thereto, and a backlight used as a light source is installed for a transmissive or semi-transmissive type device. Thus, the fabrication of liquid crystal display device is completed (S7).
Unfortunately, the above-explained liquid crystal display device according to the related art has the following problems.
If the liquid crystal display panel is a small and thin, the number of scribing process increases as the panel size decreases. As a result, the strength of the substrate, which is thinned, becomes weak, whereby the substrate is vulnerable to breakage along the scribing lines when the substrate is transported after the scribing process or the breaking process is carried out on the substrate.
Moreover, the above-problems are associated with the general LCD panel as well.